In general, the tape used at present as a magnetic recording medium is mostly a so-called metal tape in which ferromagnetic metal powder is coated on a polyester base film. However, this tape, which employs a binder, is limited with request forming a film of a magnetic layer, capable of obtaining a high recording density. Recently, there has been highlighted a metallized tape having a metallic film formed by a so-called gaseous phase plating method typified by vacuum deposition not needing any binder.
As the metallized tape of the type described above, there has been proposed a metallized tape having as the recording magnetic material a film of a cobalt-nickel magnetic alloy containing from 20 to 30 wt%Ni.
As regards the high recording density, this magnetic recording medium has an outstanding performance, but on the contrary, it has the disadvantages that the Co-Ni magnetic alloy magnetic layer is very expensive, the medium itself is brittle and tends to initiate cracks, and it is easily corroded under high temperature and high humidity, whereby the magnetic property is deteriorated, i.e. it is unfavorable in so-called corrosion resistance and the like, so that the medium has limited durability.
To improve the corrosion resistance from among the above-described problems, there have been studied protective layers obtained by coating the magnetic layer with a metal having high corrosion resistance and by applying a rustproof high polymeric substance into the magnetic layer. However, these treatments still prove unsatisfactory in their effects. The reason is that, since a Co-Ni magnetic alloy is very brittle, in producing the magnetic recording medium and during use, very small cracks are initiated, whereby even the protective layer is broken off and thus fails in providing protection against corrosion. The aforesaid cracking generates noises and considerably lowers the durability of the medium in cooperation with the unsatisfactory corrosion resistance. Consequently, in order to obtain a metallic film type magnetic recording medium satisfactory durability, it is necessary to form a magnetic layer having a satisfactory corrosion resistance in the magnetic recording layer and having a high toughness.
However, there has heretofore been known no metallic film type magnetic recording medium having as a magnetic recording layer a ferromagnetic layer with the magnetic property needed for acquiring a high recording density, as well as a corrosion resistance necessary from the viewpoint of durability, and acceptable mechanical properties.